1. Field of the Invention
The present invention relates to hydraulic pumps or motors, and more particularly to a hydraulic pump or motor with a rotary cylinder barrel for plungers to axially reciprocate.
2. Description of the Prior Art
As shown in FIG. 2 of the drawings, a conventional axial plunger pump or motor includes a housing 3 composed of a housing body 1 closed by an end wall block 2 secured thereto in a fluid-tight manner to form therein a cavity 3A to be filled with hydraulic fluid for lubrication. Disposed within the housing cavity 3A is a rotary cylinder barrel 5 which is splined to a drive shaft 4 rotatably mounted within the housing 3. The cylinder barrel 5 is formed with a plurality of circumferentially equally spaced cylinders 5A in which a corresponding number of plungers 11 are axially slidably disposed for reciprocation. The cylinder barrel 5 is axially movable on the drive shaft 4 and has a forward end face slidable in contact with a valve plate 6 under the load of a compression coil spring supported thereon. The valve plate 6 is secured in place to an internal surface of the end wall block 2, the valve plate being formed with a semi-circular suction slot 8 and a semi-circular discharge slot 10 respectively in open communication with inlet and outlet passages 7 and 9 in the end wall block 2. The suction and discharge slots 8 and 10 are arranged to be communicated with the barrel cylinders 5A for suction and discharge operation of hydraulic fluid. An inclined swash plate 14 is tiltably supported at its opposite sides on the housing body 1 for frictional engagement with shoes coupled with each spherical head of plungers 11. During rotation of the cylinder barrel 5, frictional engagment of the plunger shoes on the inclined swash plate 14 causes pumping action by reciprocating the plungers 11 in the barrel cylinders 5A.
In the axial plunger pump or motor, the housing cavity 3A is filled with lubricant of the same kind as hydraulic fluid supplied into the barrel cylinders 5A for lubrication of sliding portions between the cylinder barrel 5 and valve plate 6 and between the swash plate 14 and plunger shoes. The hydraulic fluid supplied in excess into the housing cavity 3A is discharged to the exterior through discharge holes 3B in the peripheral wall of housing body 1. For supply of the lubricant, an oil supply plug 13 is threaded into a shoulder of housing body 1 to be manually removed when it is desired to supply the lubricant into the housing cavity 3A. In the case that the plunger pump or motor is installed in a limited space, however, the operation for supply of the lubricant becomes very difficult and troublesome.